Machine for grinding and making ready printing plates



July 2, 1940. K. KRUGER Er AL 2,205,229

IACHINE FOR GRINDING AND MAKING READY PRINTING PLATES Fi1ed Nov-. 26, 1958 :5 shuts-sheet 1 fra gvi fi July 2, 1940. K. KRUGER ET AL IIACHINE FOR GRINDING AND BAKING READY PRINTING PLATES Filed Nov. 26, 1938 3 Slants-Sheet 2 u y 2, 1940- N K. KRUGER ET AL 2,206,229

MACHINE FOR GRINDING AND HAKING READY PRINTING PLATES Filed Nov. 26, 1938 3 Slants-Sheet 3 Fig. 5

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Patented July 2, 1940 I UNITED STATES PATENT OFFICE MACHINE FOR GRINDING AND MAKING READY PRINTING PLATES pany of Germany.

' Application November 26, 1938, Serial No. 242,500

In Germany November 14, 1936 r 11 Claims.

The object of the invention is to provide a machine for grinding and making ready rubber printing plates in the operation of which the front side of the plate can be observed during the grinding of theback side, so that a satisfactory treatment of the plate is assured.

In grinding machines previously known the printing plate lies with the picture or type downward and the rear side of the printing plate is operated 'upon by a grinding wheel from above, so that observation of the front side during the grinding process is not possible.

There is a grinding device for printing plates in which the tool holder is mounted so as to be movable in vertical direction with reference to the printing plate and the grinding tool is driven through a flexible shaft. This machine is the grinding device which serves for removing material. from individual places on metal printing plates. Accordingly the grinding device works upon the upper side of the printing plate from above. According to the invention a grinding wheel is mounted in a supporting table so that it works upon the back side of the printing plate resting upon the table, while those parts of the back side of the printing plate which require grinding are pressed down from above against the grinding wheel by means of a stamp.

In accordance with a further development of the invention a rotary stamp head is provided with a plurality of pressing faces of different size and shape, which can be selectively brought into operative position. and which are moved against the. printing plate by suitable means, such as a hand or foot lever. in accordance with the invention the minimum distance from the grinding wheel to the stamp face can be adjusted to fractions of a millimeter by means of a fine thread, according to the desired thickness of the rubber printing plate,

The supporting table preferably has openings through which the rubber dust formed in. the grinding process can be sucked away downward.

The invention is illustrated by one embodiment shown in the accompanying drawings, wherein-- Fig. 1 is a side view, partly in section, ofa

an auxiliary device for grinding the lines of the printing plate, a portion of the table appearing in vertical section; and i Fig. 6 is a similar view showing another form of grinding device for type. d

To a supporting. table i is rigidly connected an arm 2, in the forward part 3 of which is a vertical bore holding a shaft i in a manner permitting longitudinal movement. The lower part of the shaft is formed as a head 5 0011- in taining a horizontal bore'lined with a bushing t. Rotatably mounted in the latter is a shaft "i of a stamp holder 3, bearing stamps l'i, it, it which can be selectively brought into the operative downwardly directed position by rotating the in stamp head and which have pressing faces of different size and contour. The stamp holder 9 is drawn against the shaft head 5 by a spring 9 and the shaft head and stamp are provided with interengaging tongue and groove devices it to we hold the stamp head in any selected position.

The end 3 of the arm 2 has an upwardly facing internally threaded cup surrounding the shaft t and into this cup is screwed an externallythreaded bushing it, which is to serve as a stop as to limit the downward stroke of the stamp head and to provide an adjustment for compensating for the wear of the grinding wheel. The shaft t is provided with a fine thread upon which is screwed a round nut Mi, which counts with the no upper face of the bushing it. The nut it bears a cap it on which is marked a scale, which co operates with a pointer it (Figs. 1 and 2) mounted on the arm he i]. thus providing ior adjustment of the nut by fractions of a miilimas eter. Fig. 1 shows the lowest position of the stamp holder d, in which the nut it rests upon the upper face of bushing it. Between the stamp ii on holder 8 and the table i is a;space which corresponds to thethickness to which the rubber to printing plate is to be ground.

The table I has on its under side a thickened flange it to which is screwed a ring-shaped 'ing member 2|. In the bearing member ii (Figs.

1 and-3) the shaft 22 of a fan wheel it is roup tatably mounted in vertical position. The fan serves to draw through the openings 24 in table I the rubber dust arising from the grinding of the rubber printing plates, which is then conveyed ofi through a conduit connected to the nipple 25. "The fan wheel shaft 22 is hollow and internally threaded at its lower end. The lower end of shaft 26 of the grinding disk 27 is externally threaded and is screwed into the threads of the shaft 22. A nut 28 serves to lock the shaft 28 I to the shaft 22, so that the rinding wheel 21 fan wheel form-a rigi unit.. A second nut 20a is fixed by a pin to the lower end of theshaft 26 and acts-both as a handle for adjusting the shaft 26 in axial direction and as a stop for limiting the axial adjustment when the grinding wheel has been' worn away to a large degree.

Upon the lower end of the fan wheel shaft 22 is fastened a belt pulley 30, which is-turned by a beltil driven by an electric motor 29; thereby the fan wheel 23 and grinding wheel 21 are' slot connection 35, 36 (Fig. 2), a lever 31, a shaft 38, and a lever 39. The thrust rod 4| acts upon a lever arm 42 fastened toa shaft 44, to which is also secured a lever arm 43. The shaft 14 is rockably mounted in the machine arm 2. The lever arm 13 has a slot 45 embracing a pin 46 which projects from the shaft 6 through a slot a in the arm head 3.

The described machine canalso be made so as to be converted at will from a machine for grinding and making ready into a type and line grinding machine. For the, latter purpose the following additional devices are provided:

At a suitable place, for example, on the side of the machine. a special electric motor 59 (Figs. and 6) is mounted, which transmits a driving motion through a flexible transmission shaft 58 to a holder 52 The holder 52 can either be mounted in place of the stamp holder 8 upon the shaft '5, or, as the example in the drawings shows, can be screwed upon one of the pressing stamps of the stamp holder 8, for instance, the stamp ii. In Fig. 5 the holder 52 is so positioned that the drive shaft lies horizontally and a conical grinding disk for working upon or producing lines can be used. In Fig. 6 the drive shaft in the holder 52 is vertical, so that a grinding rod for working or grind ing individual type can be used.

When the device is used for grinding type or lines, thedrive of the grinding wheel 2! is stopped.

- The manner of operation of the described machine, in brief recapitulation, is as follows:

By means of the bushing l2 an adjustment can be made to compensate for wear of the grinding wheel 21, so that the indication of the pointer it upon the scale on cap it will be accurate.

' By means of the cap it fastened to the nut 54 that one of the three pressing stamps ll, I8, 20 which is in operative position can be finely ad- :Iusted according to the desired thickness of the printing plate being worked upon. The latter is laid upon the table I with its back side down over the grinding wheel 21, so that the portion to be' ground lies under the stamp l1, ID, or 20 which is in operative position.

when the adjustment has been completed, the operative stamp is pressed toward the grinding wheel 21 by the lever 33, so that the back side of the printing plate is ground on. The switching on of the electric motor 28 for driving the grinding wheel 21 and the fan wheel 22 can be made andaaoaaeo g 'to take place simultaneously with the movement of lever 33, or by a special switch device. During the work the rubber printing plate can easilyvbe observed from above.

If individual lines or type of the printing plate are to be worked upon, the holder 52 is screwed on to the stamp holder 8 and, according to the desired method of operation, a grinding disk like Fig. 5, or a grinding rod like Fig. 6 is set on. We claim:

1. In a grinding machine for rubber printing plates, atable to support the printing plate having .a hole therein, a grinding wheel mounted in said hole so that its face is approximately at the level of the surface of the table, a stamp head mounted for up and down movement above the table and having a plurality of faces of different area, said stamp head being also rotatable'to bring a selected one of said faces into position to press a portion of the printing plate against the grinding wheel, and means for moving the stamp head up and down. I

2. In a grinding machine for'rubber printing plates, a table to support they printing plate having a hole therein, a grinding wheel mounted in said hole so that its face is approximately at the level of the surface of the table, a stamp head mounted for up and down movement above the table and having a face adapted to press a portion of the printing plate against the grinding wheel, manipulative means for moving the stamp head up and down, means for limiting the movement of I and down movement on said arm and having a face adapted to press a portion of the printing plate against the grinding wheel, a second grinding. means, and meanswhereby the latter can be supported from said arm so as to be movable into and. out of contact with the supper surface of the printing plate.

4. In a. grinding machine for rubber printing plates, a table to support the printing plate having a hole therein, a grinding wheel mounted in said hole so that its face is approximately at the level of the surface of the table, means movably supported abovethe table for pressing the printing plate to the grinding wheel, said table having openings therethrough adjacent said grinding wheel hole, and means for drawing air downward through said openings.

5. In a grinding machine for rubber printing plates, a table to support the printing plate having a hole therein, a grinding wheel mounted in said hole so that-its face is approximately at the level of the surface ,ofthe table, an arm rigidly overhanging said table having a vertical bore in its forward part, a vertical shaft movable longitudinally in said bore, and a stamp head comprising a supporting shaft, said vertical shaft having a horizontal bore at its lower end to receive said stamp head shaft, said .stamp head having a pressing face adapted to push a portion ing a hole therein, a grinding wheel mounted in said hole so that its face is approximately at the level, of the surface of the table, an arm rigidly overhanging said table having a vertical bore in its forward part, a vertical shaft movable longitudinally in said bore, a stamp head comprising a supporting shaft, said vertical shaft having are provided with interengaging tongue and groove devices to hold said stamp head in a selected position, and a spring is provided to hold said stamp head against said vertical shaft.

8. In a grinding machine for rubber printing plates, a table to support the printing plate having a hole therein, a grinding wheel mounted in said hole so that its face is approximately at the level of the surface of the table, an arm rigidly overhanging said table having a vertical bore in its forward part, a. vertical shaft movable longitudinally in said bore, a stamp head comprising a supporting shaft, said vertical shaft having a horizontal bore at its lower end to receive said stamp head shaft, said stamp head having a pressing face adapted to push a portion of the printing plate against said grinding wheel, said vertical shaft being threaded'with fine threads at its upper end, a nut screwed onto said threads, said arm having an upwardly opening internally threaded cup surrounding said vertical shaft below said nut, and an externally threaded bushing screwed into the threads of said cup and serving as a stop limiting the downward movement of said vertical shaft.

40 9. A grinding machine as described inclaim 8,

wherein said nut is provided with a cap marked with a scale, and said arm is provided with a pointer co'actlng with said scale.

10. In a grinding machine for rubber printing plates, 8. table to support the printing plate having a hole therein, .a grinding wheel mounted in said hole so that its face is approximately at the level of the surface of the table, means movably supported above the table for pressing the printing plate to the grinding wheel, said table having openings thereth ough adjacent said grinding wheel hole and a thick flange on its lower side surrounding said openings, a bearing member having a flange fixed to said thickened flange, a suction fan rotatably mounted in said bearing member below said openings, and means for rotating said fan.

11. In a grinding machine for rubber printing plates,'a table to support the printing plate having a hole therein, a grinding whe mounted in said hole so that its face is approximately at the level of the's'urface of the table, means movably supported above the table forpressing the printing plate to the grinding wheel, said table having openings therethrough adjacent said grinding wheel hole and a thick flange on its lower side surrounding said openings, a bearing member having a flange fixed to said thickened flange, a suction fan below said openings having an internally threaded hollow shaft rotatably mounted in said bearing member, said grinding wheel having an externally threaded shaft screwed into said hollow shaft, means for locking said grinding wheel shaft in a set position in said hollow shaft, and means for rotating the unit comprising said fan and said grinding wheel.

KARL KRt'iGER. LAMBERT KOOP. 

